Multi-stage centrifugal pump unit

Abstract

A multi-stage centrifugal pump assembly includes at least two impellers ( 2, 6 ) and two impeller groups ( 4, 8 ) which are consecutive in a flow direction and each with at least one impeller ( 2, 6 ). A backflow channel ( 24 ) connects an exit side of the first impeller group ( 4 ) to an entry side thereof is located in a first impeller group ( 4 ) of the two impeller groups ( 4, 8 ).

The invention claimed is: 
     
       1. A multi-stage centrifugal pump assembly comprising:
 at least two impellers ( 2 ,  6 ); 
 two impeller groups, including a first impeller group ( 4 ) and a second impeller group ( 8 ), positioned consecutively on a same shaft in a flow direction that flows from an inlet connection ( 10 ) of the pump assembly, with each impeller group having at least one of the at least two impellers ( 2 ,  6 ); and 
 a backflow channel ( 24 ) located entirely within the first impeller group ( 4 ) having an entrance positioned between the first impeller group ( 4 ) and the second impeller group ( 8 ), 
 wherein at least one valve ( 38 ) for closing the backflow channel ( 24 ) is located in the backflow channel ( 24 ) at an exit side of the first impeller group ( 4 ), and 
 wherein the first impeller group ( 4 ) at an exit side thereof comprises a separating element ( 20 ) for separating air and other fluid, and 
 wherein the first impeller group ( 4 ) is designed with at least two-stages with two impellers ( 2 ) arranged one after the other in the flow direction, wherein one of the two impellers is an impeller of the at least two impellers. 
 
     
     
       2. The multi-stage centrifugal pump assembly according to  claim 1 , wherein the backflow channel ( 24 ) runs out into a suction port ( 28 ) of a first stage of the first impeller group ( 4 ). 
     
     
       3. The multi-stage centrifugal pump assembly according to  claim 1 , wherein the at least one valve ( 38 ) is designed in a manner such that on reaching a predefined fluid pressure in the backflow channel ( 24 ), the at least one valve ( 38 ) closes the backflow channel ( 24 ). 
     
     
       4. The multi-stage centrifugal pump assembly according to  claim 1 , wherein the separating element ( 20 ) is arranged relative to the backflow channel ( 24 ) such that the fluid exiting from the separating element ( 20 ) enters into the backflow channel ( 24 ). 
     
     
       5. The multi-stage centrifugal pump assembly according to  claim 1 , wherein a check valve is arranged on the entry side of the first impeller group ( 4 ). 
     
     
       6. The multi-stage centrifugal pump assembly according to  claim 1 , wherein at least one fluid storage device ( 48 ) is arranged between the first impeller group ( 4 ) and the second impeller group ( 8 ). 
     
     
       7. The multi-stage centrifugal pump assembly according to  claim 6 , wherein the at least one fluid storage device ( 48 ) is an annular pot with an open upper side which surrounds a shaft ( 16 ) driving the impellers ( 2 ,  6 ). 
     
     
       8. The multi-stage centrifugal pump assembly according to  claim 1 , wherein each impeller of the second impeller group ( 8 ) is arranged in one or more stage modules, wherein all stage modules have the same axial height, and the at least one impeller ( 2 ) of the first impeller group ( 4 ) is arranged in a stage module which has an axial height which corresponds to an axial height or an integer multiple of an axial height of a stage module of the second impeller group ( 8 ). 
     
     
       9. The multi-stage centrifugal pump assembly according to  claim 8 , wherein fluid storage devices ( 48 ) or spacer elements, which are arranged between the two impeller groups ( 4 ,  8 ), have an axial height which corresponds to an axial height or an integer multiple of the axial height of the stage module of the second impeller group ( 8 ). 
     
     
       10. A multi-stage centrifugal pump assembly comprising:
 at least two impellers ( 2 ,  6 ); 
 two impeller groups comprising a first impeller group ( 4 ) and a second impeller group ( 8 ) arranged on a same shaft, each impeller group having at least one of the at least two impellers ( 2 ,  6 ); and 
 a backflow channel ( 24 ) located within the first impeller group ( 4 ) having an entrance positioned between the first impeller group ( 4 ) and the second impeller group ( 8 ), 
 wherein at least two fluid storage devices ( 48 ) are arranged in a manner such that an exit opening of a second fluid storage device ( 48 ) runs out into an opening of a first fluid storage device ( 48 ). 
 
     
     
       11. The multi-stage centrifugal pump assembly according to  claim 1 , wherein the separating element ( 20 ) comprises a peripheral wall ( 22 ), a central region close to the shaft ( 16 ), and a peripheral region close to the peripheral wall ( 22 ), and wherein within the separating element ( 20 ) fluid is accelerated radially outwardly, so that air exits from the separating element ( 20 ) in the central region, and the other fluid exits from the separating element ( 20 ) in the peripheral region. 
     
     
       12. The multi-stage centrifugal pump assembly according to  claim 11 , wherein the peripheral wall ( 22 ) has an upper edge, and the other fluid exiting from the peripheral region flows over the peripheral wall ( 22 ) at the upper edge thereof. 
     
     
       13. The multi-stage centrifugal pump assembly according to  claim 11 , wherein the separating element ( 20 ) is arranged relative to the backflow channel ( 24 ) such that the other fluid exiting from the separating element ( 20 ) enters into the backflow channel ( 24 ). 
     
     
       14. The multi-stage centrifugal pump assembly according to  claim 12 , wherein the separating element ( 20 ) is arranged relative to the backflow channel ( 24 ) such that the other fluid exiting from the separating element ( 20 ) enters into the backflow channel ( 24 ). 
     
     
       15. A multi-stage centrifugal pump assembly comprising:
 at least two impellers ( 2 ,  6 ); 
 two impeller groups, including a first impeller group ( 4 ) and a second impeller group ( 8 ), positioned consecutively on a same shaft in a flow direction that flows from an inlet connection ( 10 ) of the pump assembly, with each impeller group having at least one of the at least two impellers ( 2 ,  6 ); and 
 a backflow channel ( 24 ) located entirely within the first impeller group ( 4 ) having an entrance positioned between the first impeller group ( 4 ) and the second impeller group ( 8 ), 
 wherein at least one valve ( 38 ) for closing the backflow channel ( 24 ) is located in the backflow channel ( 24 ) at an exit side of the first impeller group ( 4 ), and 
 wherein the first impeller group ( 4 ) at an exit side thereof comprises a separating element ( 20 ) for separating air and other fluid, and 
 wherein at least one fluid storage device ( 48 ) is arranged between the first impeller group ( 4 ) and the second impeller group ( 8 ), and 
 wherein the at least one fluid storage device ( 48 ) comprises at least one exit opening arranged in a manner to lie opposite an entry opening of the backflow channel ( 24 ) in a manner such that fluid can flow out of the at least one fluid storage device ( 48 ) into the backflow channel ( 24 ). 
 
     
     
       16. A multi-stage centrifugal pump assembly comprising:
 at least two impellers ( 2 ,  6 ); 
 two impeller groups, including a first impeller group ( 4 ) and a second impeller group ( 8 ), positioned consecutively on a same shaft in a flow direction that flows from an inlet connection ( 10 ) of the pump assembly, with each impeller group having at least one of the at least two impellers ( 2 ,  6 ); and 
 a backflow channel ( 24 ) located entirely within the first impeller group ( 4 ) having an entrance positioned between the first impeller group ( 4 ) and the second impeller group ( 8 ), 
 wherein at least one valve ( 38 ) for closing the backflow channel ( 24 ) is located in the backflow channel ( 24 ) at an exit side of the first impeller group ( 4 ), and 
 wherein the first impeller group ( 4 ) at an exit side thereof comprises a separating element ( 20 ) for separating air and other fluid, and 
 wherein at least two fluid storage devices ( 48 ) are arranged between the first impeller group ( 4 ) and the second impeller group ( 8 ) in a manner such that an exit opening of a second fluid storage device ( 48 ) runs out into an opening of a first fluid storage device ( 48 ).